In batch processing, the customary practice is to place the product in a processing vessel wherein it is treated by a fluid already contained in or later introduced into the vessel. Where the processing is carried out at non-ambient pressure or where the processing fluid should not be exposed to the ambient, the vessel is hermetically sealed by a cover or the like.
For the most part, food products are processed in batches by contacting the product with a hot, heat transfer fluid such as water or steam. Pressure cookers are commonly used where large quantities of a product are to be cooked as, for example, in a canning plant. In one such type of cooker the food is carried through a steam filled pressure vessel by means of a screw or augur. Decompression compartments are located at the ends of the vessel to permit the continuous passage of the product into and out of the vessel. Such cookers are not only expensive to manufacture and maintain, but they are suitable only for use with bulk-type items.
There is a need for a conveyorized processing apparatus and method wherein batches of a product are separately processed on a continuous basis. Such apparatus will enable the processing of fragile products and will, in addition, permit the use of a sequence of different processing steps in an automated system. When used in preparing frozen food, for example, on a continuous basis the food may be initially defrosted at about ambient pressure and then cooked at an elevated pressure.